Thanks alot guys, appreciate the feedback. He is struggling on which to build now because in the near future he is going to build a defensive edge canyon rifle. Currently he has a ton of 338rum brass,dies etc, so building an edge would involve additional start up costs. My vote is to build this one into an edge and later the canyon rifle so he will have a matched set? with those circumstances, what would you do? he is not a member but he is on here at least a half hour every day so he will see your responses. Thanks again

You will not notice a difference between the 338 RUM and 338-300 RUM in accuracy, shooting or hunting. If you hunted with the 338-300 RUM one year and the next hunted with the 338 RUM in identical rifles you would not be able to tell the difference in any way performance wise. After extensive testing back in 2001 when the 338 RUM came out they proved to be so close the individual barrels made more difference than the cartridges. They shoot virtually the same accuracy loads and velocities. That is why I quit doing the 338-300 RUM in 2001 when the 338 RUM came out. I just went with the factory cartridge after doing the 338-300 RUM since late 98 or so. Most accuracy loads in either cartridge will average 2735-2785 fps in a 26" barrel.

There is about a ten grain powder difference between the 340 wby and 338-300 RUM to gain about 125 fps. There is about a 16 grain powder difference between the 338-300 RUM and the 338-378 wby to gain about 250 fps. Both the 338 RUM and the 338-300 RUM shoot accuracy loads of 91-93 grains of H-1000. How much velocity difference do you think there will be?

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